Core files can now work with frozen string literals, both from magic comments and from the CLI option.

Author: nirvdrum

CHANGELOG.md

@@ -28,6 +28,8 @@ Changes:
 Performance:
 
 * Sped up accesses to native memory through FFI::Pointer.
+* All core files now make use of frozen `String` literals, reducing the number
+  of `String` allocations for core methods.
 
 # 1.0 RC 10
 

src/main/java/org/truffleruby/parser/BodyTranslator.java

@@ -2880,10 +2880,7 @@ public RubyNode visitStrNode(StrParseNode node) {
         final Rope rope = context.getRopeCache().getRope(node.getValue(), node.getCodeRange());
         final RubyNode ret;
 
-        // isFrozen() is set with the magic frozen_string_literal comment or the command line flag.
-        // For the command line flag, we do not want to apply it to the core library files.
-        // TODO (eregon, 28 Feb 2018): we should respect the magic comment in core (although not used currently).
-        if (node.isFrozen() && !inCore()) {
+        if (node.isFrozen()) {
             final DynamicObject frozenString = context.getFrozenStringLiteral(rope);
 
             ret = new DefinedWrapperNode(context.getCoreStrings().EXPRESSION,